US6646897B1 - Method and system of slow output voltage ramp control for a power supply - Google Patents
Method and system of slow output voltage ramp control for a power supply Download PDFInfo
- Publication number
- US6646897B1 US6646897B1 US10/137,458 US13745802A US6646897B1 US 6646897 B1 US6646897 B1 US 6646897B1 US 13745802 A US13745802 A US 13745802A US 6646897 B1 US6646897 B1 US 6646897B1
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- voltage
- output
- power supply
- current sense
- controller
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
- H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
- H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
- H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
- H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/33507—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/0003—Details of control, feedback or regulation circuits
- H02M1/0025—Arrangements for modifying reference values, feedback values or error values in the control loop of a converter
Definitions
- the present invention relates generally to power supplies and particularly to power supply output control.
- Integrated circuits typically have varying requirements for power supply voltages. Various integrated circuits may require different power supply voltage levels and different ramp-up times for the power supply voltages.
- One method for controlling the ramp-up time for a power supply is to couple a pass transistor to the output of the power supply.
- the transistor turns on slowly, feeding current to the load at a reduced rate, while the power supply ramps up at a much quicker rate. Once the power supply output is at its maximum, the transistor appears as a short circuit to the power supply.
- transistors typically do not make a perfect short and, therefore, waste some power supply energy in the form of heat.
- the heat dissipation of the pass transistor may be reduced by using a transistor that has a very low “on” resistance. These transistors are typically very expensive, thus adding to the cost of the power supply. There is a resulting need for a power supply that can economically control the ramp-up time of its output voltage without wasting power supply energy.
- Embodiments of the present invention provide a slow output voltage ramp-up by controlling the output voltage ramp-up on the primary side of the power supply's transformer.
- the power supply comprises a feedback voltage that is coupled to the output voltage of the power supply.
- the feedback voltage is proportional to the output voltage.
- a controller has a current sense input, a voltage feedback input, and a control output.
- the voltage feedback input is coupled to the feedback voltage and the controller adjusts a current sense threshold in response to the feedback voltage level.
- a control circuit apparatus is coupled to the current sense input of the controller.
- the control circuit apparatus comprises an offset voltage generator and a timer controlled switch coupled to the offset voltage generator. The timer-controlled switch applies the offset voltage to the current sense input during a predetermined time interval set by the current sense threshold. This turns the control output on during the predetermined time interval.
- An output control switch is coupled to the control output. The switch turns on when the control output is on.
- FIG. 1 shows a block diagram of one embodiment of a power supply of the present invention.
- FIG. 2 shows a circuit schematic of one embodiment of the power supply output ramp control circuit apparatus in accordance with the power supply of FIG. 1 .
- FIG. 3 shows a plot of an output voltage of a typical prior art power supply compared to an output voltage of the power supply of the present invention.
- FIG. 4 shows a plot of an output voltage of the power supply of the present invention that provides a dual slope output voltage.
- Embodiments of the present invention provide a power supply output voltage ramp control circuit apparatus with a slow output ramp-up while not using energy consuming control circuits on the output. This is accomplished by controlling the output voltage ramp-up on the primary side of the power supply's transformer.
- FIG. 1 illustrates a block diagram of one embodiment of a power supply ( 100 ).
- the power supply outputs a regulated +5 VDC voltage.
- Alternate embodiments use other power supply outputs.
- the embodiments of the present invention are not limited to any one voltage output.
- the power supply ( 100 ) is comprised of a pulse width modulation (PWM) controller ( 145 ) that provides control of the output voltage ( 135 ) of the power supply.
- PWM pulse width modulation
- the PWM controller ( 145 ) functions are incorporated on an integrated circuit.
- An example of such a PWM controller is UCC2813 Low Power Economy BiCMOS Current Mode PWM manufactured by UNITRODE. This part is for purposes of illustration only and does not limit the embodiments of the present invention to this particular part.
- PWM is a method for modulating the duty cycle of a square wave to encode a specific analog signal level.
- the voltage or current source is supplied to a load by means of a repeating series of on and off pulses.
- the on time is the time during which the DC supply is applied to the load and the off time is the time period during which the DC supply is not applied to the load. Since PWM is well known in the art, it is not discussed further herein.
- a 100 kHz modulating frequency is used.
- the embodiments of the present invention are not limited to any one operating frequency. Alternate embodiments use different modulating frequencies and still remain within the scope of the embodiments of the present invention.
- the PWM controller ( 145 ) has a power supply input ( 101 ) referred to as V cc to which a predetermined supply voltage is applied. In one embodiment, this supply voltage is +5V above the ground pin. Alternate embodiments use other supply voltage levels.
- the PWM controller ( 145 ) is further comprised of an “ISENSE” input ( 104 ).
- the ISENSE input ( 104 ) is a current sense input that is used to control the output of the PWM controller based on the voltage applied to this input. If the voltage that is applied to the ISENSE input ( 104 ) is less than a threshold, the output ( 103 ) of the PWM controller ( 145 ) goes substantially close to Vcc. If the voltage that is applied to the ISENSE input ( 104 ) is greater than the threshold, the output ( 103 ) of the PWM controller ( 145 ) is off or substantially close to 0V.
- a “VFEEDBACK” input ( 105 ) of the PWM controller ( 145 ) is used to adjust the current sense threshold.
- the output ( 103 ) of the PWM controller ( 145 ) in response to the ISENSE input ( 104 ) voltage, controls the operation of a transistor ( 112 ) that acts as an output control switch.
- the output of the PWM controller ( 145 ) is coupled to the gate of the transistor ( 112 ).
- the on time of the transistor ( 112 ) sets the duty cycle of the power supply ( 100 ).
- the transistor ( 112 ) is a field effect transistor (FET). Alternate embodiments may use other types of transistors in place of the FET.
- FET field effect transistor
- this transistor ( 112 ) When this transistor ( 112 ) is turned on by the PWM controller ( 145 ), energy is stored in the primary ( 117 ) winding of the transformer ( 116 ). When the transistor is turned off, energy is released from the secondary ( 118 ) winding of the transformer ( 116 ) and is transferred to the power supply output ( 135 ) and the load ( 140 ).
- a diode ( 120 ) may be used on the output of the secondary ( 118 ) side of the transformer ( 116 ) to act as a rectifier for the output signal.
- This implementation of a power supply is commonly referred to as a “Flyback”.
- the embodiments of the present invention are not limited to any of these elements. Other circuits may perform substantially the same function as the transformers, capacitors, and diodes illustrated in FIG. 1 .
- a current sense node ( 110 ) voltage is generated across a primary current sense resistor ( 115 ).
- the node voltage ( 110 ) is the ISENSE input to the PWM controller ( 145 ). This voltage increases until it reaches a threshold set by the PWM controller ( 145 ) via a feedback voltage.
- the threshold set by the PWM controller ( 145 ) is varied based on a feedback voltage ( 111 ) that is fed back from the power supply output ( 135 ).
- the feedback voltage ( 111 ) is input to the “VFEEDBACK” input ( 105 ) of the PWM controller ( 145 ).
- the feedback voltage ( 111 ) is used by the PWM controller ( 145 ) to regulate the output. If the feedback voltage ( 111 ) goes below a predetermined voltage, the current threshold is increased. In one embodiment, this predetermined voltage may be 4.5V. If the feedback voltage ( 111 ) goes above a predetermined voltage, the current threshold is decreased. In one embodiment, this predetermined voltage may be 5.0V.
- the PWM controller ( 145 ) adjusts the ISENSE limit on every cycle of the output signal (e.g., every 10 microseconds in one embodiment) in order to regulate the feedback voltage.
- VFEEDBACK When the power supply is first powered-up, VFEEDBACK is zero. This causes the highest possible limit to be set for ISENSE. In one embodiment, the limit is 1 Volt. If left uncontrolled, the output of the power supply will ramp-up quickly to its maximum value.
- the ramp control circuit apparatus of the present invention artificially raises the ISENSE voltage at power-up in order to control the ramp-up of the output voltage by bringing the ISENSE node closer to the 1V limit.
- the ramp control circuit apparatus is comprised of an ISENSE offset voltage ( 126 ) that is selectively applied to the ISENSE input ( 104 ) of the PWM controller ( 145 ).
- a timer-controlled switch ( 125 ) selectively applies the ISENSE offset voltage ( 126 ) to the ISENSE input ( 104 ).
- the ISENSE offset voltage is +0.45V. Alternate embodiments use different offset voltages, depending on the implementation and speed of output voltage ramp-up desired.
- the timer portion of the timer-controlled switch is a resistor/capacitor network that has a certain RC time constant based on the values of these elements. The operation of this timer is discussed subsequently in greater detail with reference to the embodiment of FIG. 2 .
- the timer-controlled switch ( 125 ) is set to apply the offset voltage ( 126 ) only until the output voltage has ramped up to a desired value.
- the timer-controlled switch ( 125 ) may be set to open at a time that depends on the desired ramp-up speed of the output voltage. In one embodiment, the switch ( 125 ) is set to open in approximately 2 milliseconds in order to keep the output of the power supply from ramping up from 0 to +5 V in less than 2 milliseconds. Alternate embodiments use other times and other peak voltages, depending on the implementation.
- the ramp control circuit apparatus may be used to generate two slopes for the output voltage ( 135 ) of the power supply.
- the timer-controlled switch ( 125 ) may be set to open when the output voltage has reached half of its maximum value. When this mid-value is reached and the switch ( 125 ) opens, the output voltage ramps up at a quicker pace. This embodiment provides a double-sloped output voltage.
- the ramp control apparatus does not use a pass transistor at the output of the power supply. Therefore, the prior art problem of too much heat dissipation does not arise.
- FIG. 2 illustrates one embodiment for implementing the ramp control circuit apparatus of FIG. 1 . This figure is for illustration purposes only since the embodiment illustrated in FIG. 1 may be implemented in multiple ways.
- the embodiment of FIG. 2 is comprised of the PWM controller ( 145 ).
- the controller is coupled to a 100 kHz oscillator ( 201 ) that supplies the operating frequency for both the controller and the switch transistor ( 112 ).
- the transistor ( 112 ) therefore, turns on and off at the 100 kHz rate.
- the output of the PWM controller ( 145 ) is coupled to the transistor's ( 112 ) gate through a resistor ( 235 ).
- Another resistor ( 236 ) tied to ⁇ 48V, sets up a voltage divider to provide the proper turn-on voltage at the transistor's gate when the output of the PWM controller ( 145 ) is on.
- V ref input of the controller ( 145 ) becomes +5V above the ground input that is coupled to the ⁇ 48V supply.
- V ref becomes +5V
- a capacitor ( 230 ) is charged through a resistor ( 225 ). Until the capacitor ( 230 ) is charged, the transistor ( 215 ) of the control circuit is on.
- control circuit transistor ( 215 ) While the control circuit transistor ( 215 ) is on, it is going to apply a sum of an offset voltage and a node voltage( 110 ) to the ISENSE input of the controller ( 145 ).
- This offset voltage is determined by a voltage divider circuit comprised of two resistors ( 210 and 237 ). In one embodiment these resistors have resistance values of 1 k Ohm and 10 k Ohm, respectively. With V ref as the voltage to be divided down, the offset voltage applied to the ISENSE input is 0.9V when the timer-controlled switch is on, rather than the normal operating offset level of 0.5V when the timer controlled switch is off. Alternate embodiments use other resistance values to generate the same or even a different offset voltage.
- the node at the biasing resistors ( 225 and 220 ) is such that the transistor ( 215 ) turns off.
- a resistor ( 205 ) is used to pull up the ISENSE input to V ref when the transistor ( 215 ) is off. This pull-up sets the overall limits on the primary side of the transformer ( 116 ).
- the ISENSE input of the controller ( 145 ) only has the voltage across the pull-up resistor ( 205 ) applied.
- the artificially elevated ISENSE voltage is gone.
- the controller ( 145 ) is now free to regulate the supply output voltage across the output capacitor ( 140 ) in a normal fashion.
- Another resistor ( 237 ) feeds in the primary current sense node ( 110 ) voltage from the primary current sense resistor ( 115 ).
- the primary current sense resistor ( 115 ) has a ramp voltage across it that is proportional to the primary current of the power supply.
- the feedback voltage ( 111 ) from the power supply output sets the current sense limit of the controller ( 145 ). If the feedback voltage is too low (e.g., 4.5V), meaning the output voltage of the supply is too low, a higher peak primary current will be allowed on the ISENSE input (i.e., the sense threshold is raised) so that the ramp voltage will go higher. This allows more energy to the transformer ( 116 ) and therefore more energy out of the transformer ( 116 ). This increases the output voltage.
- the feedback voltage is too low (e.g., 4.5V)
- the sense threshold is raised
- the controller ( 145 ) lowers the sense threshold on the ISENSE input. This turns on the switch transistor ( 112 ) to allow the primary current to increase.
- the output voltage ramp-up slope can be varied by changing elements of the control circuit apparatus. By changing the values of the resistor ( 225 ) and capacitor ( 230 ) in the control circuit, the point at which the transistor ( 215 ) turns off is changed. Thus, the point at which the power supply is allowed to ramp up naturally changes.
- FIG. 3 illustrates a plot of an output of a typical power supply ( 301 ) without output voltage ramp control compared to an output voltage ( 305 ) with the output voltage ramp control. Without the control ( 301 ), the output voltage ramps up quickly from 0V to the power supply voltage maximum (e.g., +5V). This may occur as quickly as 2 to 5 microseconds.
- the power supply voltage maximum e.g., +5V
- the output voltage ( 305 ) ramps up slowly. It may take one to two milliseconds to reach the regulated voltage of the supply.
- FIG. 4 illustrates a plot of an output of a power supply of the present invention with the output voltage ramp control circuit apparatus set to provide two output voltage slopes ( 401 and 405 ).
- the output voltage ramps up slowly ( 401 ) such that it may take one to two milliseconds to reach the regulated voltage of the supply.
- the capacitor of the control circuit has charged and turned off the transistor ( 403 )
- the power supply output ramp control circuit apparatus of the present invention provides control of a power supply output.
- the control circuit apparatus may be set to provide a slow output voltage ramp-up or a multiple slope output voltage. This is accomplished without the need for expensive pass transistors or other elements connected to the power supply output that waste output power.
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US10/137,458 US6646897B1 (en) | 2002-04-30 | 2002-04-30 | Method and system of slow output voltage ramp control for a power supply |
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US10/137,458 US6646897B1 (en) | 2002-04-30 | 2002-04-30 | Method and system of slow output voltage ramp control for a power supply |
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Cited By (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20040257839A1 (en) * | 2003-06-18 | 2004-12-23 | Ta-Yung Yang | Primary-side regulated pulse width modulation controller with improved load regulation |
US20050219871A1 (en) * | 2004-03-30 | 2005-10-06 | Hong-Chun Li | Piecewise on-time modulation apparatus and method for a power factor corrector |
US6972969B1 (en) * | 2004-08-19 | 2005-12-06 | Iwatt, Inc. | System and method for controlling current limit with primary side sensing |
US20060091868A1 (en) * | 2004-10-29 | 2006-05-04 | Wickersham Robert D | Switching regulator frequency control |
US20060256588A1 (en) * | 2004-09-29 | 2006-11-16 | Weibin Chen | Current overloading proof switch power supply and its IC |
US20080205087A1 (en) * | 2007-02-27 | 2008-08-28 | Arlaindo Vitug Asuncion | Power supply feedback control using sensed duty cycle |
US20080265791A1 (en) * | 2007-04-26 | 2008-10-30 | Himax Technologies Limited | Backlight module and current providing circuit thereof |
US20110110125A1 (en) * | 2005-07-08 | 2011-05-12 | Power Integrations, Inc. | Method and apparatus to limit maximum switch current in a switching power supply |
US20120235664A1 (en) * | 2011-03-18 | 2012-09-20 | Yan Dong | Voltage converters with reduced output frequency variations and associated methods |
US20140210377A1 (en) * | 2013-01-28 | 2014-07-31 | Dialog Semiconductor Gmbh | Converter One Pin Sensing |
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JP2006353032A (en) * | 2005-06-17 | 2006-12-28 | Toyota Motor Corp | Voltage conversion device |
US7457138B2 (en) * | 2005-07-14 | 2008-11-25 | Semiconductor Components Industries L.L.C. | Single pin multi-function signal detection method and structure therefor |
US8064230B2 (en) | 2008-09-09 | 2011-11-22 | Infineon Technologies Austria Ag | System and method for power conversion |
US8700939B2 (en) * | 2009-04-30 | 2014-04-15 | Dell Products L.P. | Methods and systems for providing indirect voltage detection in a power supply |
TWI502866B (en) * | 2013-10-29 | 2015-10-01 | Richtek Technology Corp | Soft start switching power converter means |
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Cited By (20)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6836415B1 (en) * | 2003-06-18 | 2004-12-28 | Systems General Corp. | Primary-side regulated pulse width modulation controller with improved load regulation |
US20040257839A1 (en) * | 2003-06-18 | 2004-12-23 | Ta-Yung Yang | Primary-side regulated pulse width modulation controller with improved load regulation |
US7436685B2 (en) * | 2004-03-30 | 2008-10-14 | Richtek Technology Corp. | Piecewise on-time modulation apparatus and method for a power factor corrector |
US20050219871A1 (en) * | 2004-03-30 | 2005-10-06 | Hong-Chun Li | Piecewise on-time modulation apparatus and method for a power factor corrector |
US6972969B1 (en) * | 2004-08-19 | 2005-12-06 | Iwatt, Inc. | System and method for controlling current limit with primary side sensing |
US7551464B2 (en) * | 2004-09-29 | 2009-06-23 | Weibin Chen | Current overloading proof switch power supply and its IC |
US20060256588A1 (en) * | 2004-09-29 | 2006-11-16 | Weibin Chen | Current overloading proof switch power supply and its IC |
US7498790B2 (en) * | 2004-10-29 | 2009-03-03 | Intel Corporation | Switching regulator frequency control |
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US20110110125A1 (en) * | 2005-07-08 | 2011-05-12 | Power Integrations, Inc. | Method and apparatus to limit maximum switch current in a switching power supply |
US8089781B2 (en) * | 2005-07-08 | 2012-01-03 | Power Integrations, Inc. | Method and apparatus to limit maximum switch current in a switching power supply |
US8325498B2 (en) | 2005-07-08 | 2012-12-04 | Power Integrations, Inc. | Method and apparatus to limit maximum switch current in a switching power supply |
US8477515B2 (en) | 2005-07-08 | 2013-07-02 | Power Integrations, Inc. | Method and apparatus to limit maximum switch current in a switching power supply |
US20080205087A1 (en) * | 2007-02-27 | 2008-08-28 | Arlaindo Vitug Asuncion | Power supply feedback control using sensed duty cycle |
US20080265791A1 (en) * | 2007-04-26 | 2008-10-30 | Himax Technologies Limited | Backlight module and current providing circuit thereof |
US7759875B2 (en) * | 2007-04-26 | 2010-07-20 | Himax Technologies Limited | Backlight module and current providing circuit thereof |
US20120235664A1 (en) * | 2011-03-18 | 2012-09-20 | Yan Dong | Voltage converters with reduced output frequency variations and associated methods |
US8872501B2 (en) * | 2011-03-18 | 2014-10-28 | Monolithic Power Systems, Inc. | Voltage converters with reduced output frequency variations and associated methods |
US20140210377A1 (en) * | 2013-01-28 | 2014-07-31 | Dialog Semiconductor Gmbh | Converter One Pin Sensing |
US9270183B2 (en) * | 2013-01-28 | 2016-02-23 | Dialog Semiconductor Gmbh | Converter one pin sensing |
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Owner name: COMMSCOPE DSL SYSTEMS LLC (FORMERLY KNOWN AS ADC D Free format text: RELEASE OF SECURITY INTEREST IN PATENTS (RELEASES RF 036718/0042);ASSIGNOR:WILMINGTON TRUST, NATIONAL ASSOCIATION;REEL/FRAME:042126/0050 Effective date: 20170317 |
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Owner name: COMMSCOPE DSL SYSTEMS LLC, NORTH CAROLINA Free format text: CHANGE OF NAME;ASSIGNOR:ADC DSL SYSTEMS, INC.;REEL/FRAME:059644/0074 Effective date: 20160101 |